The formation of insulating and moisture barriers in various fields has become increasingly important with the advent of synthetic-resin and like systems adapted to polymerize or two form a film in situ. For example, it is desirable to seal a concrete structure, e.g. a roof, platform, deck, floor or wall, against penetration of moisture and even against the penetration of water with a hydrostatic head. While laminating the surface with foils or slabs or other materials has proved to be effective in many cases, these methods are often prohibitively expensive. Efforts have been made to coat, by spraying or painting, the support surface of concrete, wood or other materials, with a layer of bituminous material or of a synthetic resin which, upon evaporation of the solvent under heat or with time, leaves a more or less continuous, flexible and impenetrable film providing a sealing action. It has been, however, difficult to use these techniques for providing sealing and insulating layers of some thickness or to use these techniques in the preparation of sealing layers designed to resist penetration of water under pressure. For example, culverts, spillways, sewage and stormdrain lines of concrete, settling tanks and the like, as well as subterranean structures such as foundations, tunnels and shafts, are often under a hydrostatic head so that the water penetrating a concrete, masonry or natural-rock wall exudes from the latter under pressure. Typical coatings of the type described, applied in the manner set forth, are incapable of withstanding the hydrostatic pressure and do not bond to the support surface with sufficient tenacity so as to be successful. Furthermore, such conventional coating systems require careful cleaning and drying of the surface to which they are applied, are relatively expensive and often have different sealing and insulating characteristics depending upon the conditions under which they are applied.
It has been proposed heretofore to provide sealing layers or coatings from a resinous emulsion by incorporating in the layer, at least on the support surface, a precipitating agent which induces coagulation, polymerization and film formation when the precipitating agent and the emulsion are brought together. The precipitating agent may be mixed with the emulsion upon the surface (e.g. using double-spray nozzles), may be added after the emulsion has been spread upon the support surface, or may be applied to the support surface before the emulsion contacts the same. The emulsion solids coagulate rapidly in the presence of the precipitating agents and are applied by spraying, fogging or pouring on the support surface. Typical precipitating agents are inorganic or organic metal salts including zinc acetate, calcium nitrate, calcium chloride or aluminum sulfate. It is also known to provide a bituminous emulsion in which a bitumen or asphaltic component is incorporated in, or incorporates, a natural or synthetic rubber latex. Here again a precipitating agent is used and is mixed with the emulsion upon the substrate. In this case, the precipitatng agents can be weakly acidic solutions or solutions of various mineral salts, e.g. calcium chloride.
While these earlier techniques may be used to deposit relatively thick layers upon a substrate for sealing them against moisture and providing thermal or electrical or acoustic insulation, difficulties are encountered because of the corrosivity of the metal salts of the layer and the fact that fluorides, sulfates and the like are detrimental to the strength of concrete. In other words, the application of conventional layers to concrete, steel-containing and related substrates is accompanied by deterioration of the substrate. It should also be noted that the conventional sealing systems are characterized by retention of moisture for long periods, a phenomenon which is detrimental to adhesion.